1. The Field of the Invention
This application relates generally to drilling tools and their methods of manufacture and use. In particular, this application relates to diamond-impregnated drilling tools that may contain elongated structures.
2. Discussion of the Relevant Art
Drill bits and other earth-boring tools are often used to drill holes in rock and other hard formations for exploration or other purposes. One type of drill bit used for such operations is an impregnated drill bit. The part of these tools that performs the drilling action (or the cutting section of the tool) is generally formed of a matrix that contains a powdered hard particulate material, such as tungsten carbide. This material is typically infiltrated with a binder, such as a copper alloy. Finally, the cutting section of these tools is typically impregnated with an abrasive cutting media, such as for example, natural or synthetic diamonds.
During drilling operations using an impregnated drill bit, the abrasive cutting media is gradually exposed as the supporting matrix material is worn away. The continuous exposure of new abrasive cutting media by wear of the supporting matrix forming the cutting section is a fundamental functional principle of impregnated drilling tools. Impregnated drilling tools may continue to cut efficiently until the cutting section of the tool is completely consumed. At that point, the tool becomes dull and must be replaced with another one.
In some cases, impregnated drilling tools may be expensive and their replacement may be time consuming, costly, as well as dangerous. For example, the replacement of a drill bit requires removing (or tripping out) the entire drill string from a hole that has been drilled (the borehole). Each section of the drill rod must be sequentially removed from the borehole. Once the drill bit is replaced, the entire drill string must be assembled section by section, and then tripped back into the borehole. Depending on the depth of the hole and the characteristics of the materials being drilled, this process may need to be repeated multiple times for a single borehole. Thus, one will appreciate that the more times a drill bit needs to be replaced, the greater the time and cost required to perform a drilling operation.
Furthermore, conventional impregnated drilling tools often have several characteristics that can add to the consumption rate of the cutting section, and therefore, increase the operating costs associated with those drilling tools. First, the binder materials in the tools may be relatively soft in comparison to the cutting media. Accordingly, the cutting section may erode and allow diamonds or other abrasive cutting media to slough off prematurely. Second, the erosion rate of the cutting section can be increased by insufficient lubrication to and around the cutting face of the tool, or the interface between the cutting section of the tool and the material being cut. An increased erosion rate can be due at least in part to the large amounts of friction and heat created at the drilling surface from the pressure and rotational speed associated with drilling operations. Third, conventional impregnated drilling tools may also be too wear resistant to expose and renew layers of the cutting section.
Accordingly, there are a number of disadvantages in conventional impregnated drilling tools that can be addressed.